$sky-size: 2000;
@function generate-snow($num) {
  $value: '#{random($sky-size)}px #{random($sky-size)}px rgba(299,299,299,1)';
  @for $i from 2 through $num {
    $value: '#{$value}, #{random($sky-size)}px #{random($sky-size)}px rgba(299,299,299,1)'
  }
  @return unquote($string: $value)
}

.snow0 {
  position: fixed;
  z-index: 1;
  top: 0;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  box-shadow: generate-snow(50);
  animation: back-fall 24s linear infinite;
}

.snow1 {
  position: fixed;
  z-index: 1;
  transform: translateY(100vh);
  top: 0;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  box-shadow: generate-snow(25);
  animation: back-fall1 24s linear infinite;
  animation-delay: 12s;
}

@keyframes back-fall {
  from {
    transform: translateY(-100vh);
  }
  to {
    transform: translateY(100vh);
  }
}

@keyframes back-fall1 {
  from {
    transform: translateY(-100vh);
    opacity: 1;
  }
  to {
    transform: translateY(100vh);
    opacity: 0;
  }
}
